Apparatus for neutralizing radiointerference on wire lines



Patented dune 3Q, i925.

LESTER M. ILGENFRITZ, GF GRANGE, NEW JERSEY, SSIGNOR T0 IEERGN EHONE ANDTELEGRAPH COMPANY, .A 'CGRPOBATXON 0F NEW' YORK.

APPARATUS FR NEUTRALIZING RADXOINTEREERENCE 0N VDB/E LNES. i

Application filed November To all whom t may concern:

Be it known that I, Lns'rnn M. ILGENFRITZ, residing atOrange, in thecounty of Essex and State oi New Jersey, have inventedcertainImprovements in Apparatus for Neutralizing Radiointert'crence on lVireLines, of which. the following is a specification.

This invention relates to transmission cir cuits, and more 'particularlyto a new and improved system for overcoming interference on signalingconductors due to radio transmission.

In carrier transmission systems in which carrier channels are superposedon ordinary signalingcoductors, interference is sometimes produced inone or more of the carrier channels due to radio signals transmitted atthe carrier frequency assigned to the channel. In order to overcome thisdifficulty, it has heretofore been proposed to balance out theinterfering frequency by impressing upon the channel a balancingfrequency of equal amplitude and opposite phase, the balancing frequencybeing obtained from the disturbing source through the medium of anauxiliary circuit which is subject to the disturb ing influence.

In applying this remedy, some difficulty has been experienced inobtaining the proper balance due to the fact that adjustments of thebalancing potential must be made both with respect tophase andamplitude, and instrumeutalities heretofore used. for obtaining suchadjustments have been of such a character that an adjustment of eitherthe phase or the amplitude results in a change in the other, so that ithas required considerable manipulation in order to obtain a balance. Itis one of the objects of the present invention to provide a systenrinwhich the phase and amplitude of the balancing potential may becontrolled each independently of the other, so that when the phase anglehas once been adjusted, changes in amplitude may thereafter be madeWithout changing the phase angle, or vice versa. rlhis object and otherobjects of the invention may be attained by means of the arrangement setforth in the following description and illustrated in the accompanyingdrawing, Figure l of Which discloses one form or' circuit arrangementfor practicing the invention..

Referring to the drawing, EFL desigao, 1922. serial ne. 602,193.

n ates a high frequency carrier transmission line terminating at acarrier station. branch leading through a low-pass iilter ,"lf' to alow-frequency line LFL and in another branch leading through a.high-pass iilter HP to the terminal carrier equipment. The carrierequipment comprises a transmitting circuit TLand a receiving circuit ELasso# ciated with the carrier branch throu'fvh the usual high frequencybalanced trans crmer 10. The transmitting' circuit TL is connected t0midpoints of the balanced transformer', and the receivingA channel RL issho-Wn as being connected to the third Winding of the l transformer, anda balance is obtained by l means of the usual balancing network MN.

The various carrier receiving channels7 such `1 as RLI, BLZ, etc., areassociated with the receiving circuit BL through suitable lilters,

such as F1, F2, etc., adapted to select the range of frequenciesassigned to each receiving channel.

lf the main line HFL is subject to interferencefrom a radio stationemploying a carrier frequencylying `Within the range of one or' thereceiving channels, as, for er:n ample, the channel RL2, it is apparentthat the interfering radio frequency will be transmitted over the lineHFL to the receiving channel BLZ .in the same manner as the modulatedcarrier frequency transmitted to said channel in the normal operationofthe carrier system. In order to balance out the interfering frequency,a radio antenna A may be provided for absorbing from the distant radiostation the same radio signals which are impressedupon the line HFL, andthis frequency may be impressed upon the channel RLS through the circuit1l in opposite phase relation, but with the same amplitude as theinterfering potentialP ln order to adjust the phase angle ci thebalancing potential, a rotary field phase adjustment device is provided.This arrangement comprises two branch circuits 13 and 11i, includingsuitable field windings 'l5 and 1G for producing the rotary lield, lncircuit with one ot the windingsj as, fer er,- amplc, the Winding 16, isa capacity Ugand in each of the branches resistances and "19 areprovided. Since the capacity l? is included in one of the branches, andnot in the other one, the component of. the ire dll channel RL,. notdisturb the phase angle obtained by the quency receivedv from theantenna iiowing through the Winding 16 will be 90 out of phase' with thecomponent flowing through the winding l5.' The resistances 18 and 19 maybe set, so that both components have the same amplitude. Consequently,the two components energizing the two field Windings and 16 will producea rotary ield which rotates at the frequency of the electromotive forceimpressed uponv the antenna A. A third Winding is placed Within theiield of infrluence of the windings l5 and 16, and, by merely shiftingthe angle of the coil 20 with respect to the field of thev coils l5 and16, any desired phase angle may be obtained for the inducedelectromotive forces in the lcircuit 1l. These electronictive forceswill, of course, have the same frequency as the electromotive forcesimpressed upon the antenna A, the phase angle being dependent only uponthe angle at which the point 20 cuts the rotar iield.

The amplitude maybe adjusted by means of a separate amplitudecontrolling device -21 Without producing'any change in the phase angleof the' balancing current, especially if the amplitude controllingdevice is of ,such a nature as to be adjustable Without producing anychange in the .impedance of the circuit 1l as viewed from the coil 20.In, order toaccomplish this result, the ampli.- tude changing device ismade up of series and snunt res1stances as indicated, the series andshunt resistances being adjustable together, so that as the seriesresistance is increased the shunt resistance is decreased. and viceversa. Under these conditions the impedance of the circuit l1 viewedfrom the coil 20 will he substantially equal to the sum ci the shuntresistance and the two resistences included in the two Wires of thecircuit. l1 below the shunt resistance. Constant impedance transmissioncontrolling devices of the type of the device 2l are well known in theart, and the theory ci such devices need not be further elucidated.

It will be apparent from this arrangement that the phase and amplitudeadjustments may be made separately in a very simple manner. For example,the phase adjustment may he made first by listening in the receivingcircuit RLZ and adjusting the angle ci the coil 20 until theinterference is reduced to a minimum. lvlhen the minimum setting hasbeen found, it will he apparent at once that this corresponds to thecondition in which the phase of the potential from the circuit 1l. isopposite to that ci the interfering potential transmitted to the circuitRL2 over the high frequency line HFL. Having made this adjustment, thedevice 21 will then be adjusted until the interfering distlubauce can.no longer be heard in. the The latter adjustment Will Aauxiliary circuitupon l. In a Wire signaling system subject to interference due to radiosignaling, an aux-V iliary circuit upon which a similar disturbingelectromotive force may be impressed for balancing purposes, deviceassociated with said auxiliary circuit for adjusting the phase of thecurrent resulting from said balaning electromotive force and a deviceassociated with said auxiliary circuit for adjusting the amplitude ofsaid current, said phase adjusting device and amplitude adjusting devicecontrolling their respective functions independently of each other.

2. ln a wire signaling system subject to interference due to radiosignaling, an auxiliary circuit upon which a similar disturbingclectromotive force may be impressed for balancing purposes, a deviceassociated with said auxiliary circuit for adjusting the phase of thecurrent resulting lfrom said balancing elcctromotive force and a deviceassociated with said auxiliary circuit for adjusting the amplitude ofsaid current, said amplitude controlling device being capable ofadjustment for controlling the amplitude Without producing any change inthe phase determined by said phase adjusting means.

3.- ln a Wire signa-ling system subject to interference due to radiosignaling, an auxiliary circuit upon which a similar disturbingelectromotive force may be impressed for balancing purposes, a deviceassociated with said auxiliary circuit for adjusting the phase of thecurrent resulting from said balancing electromotive force and and adevice associated With said auxiliary circuit for adjusting theamplitude of said current, said phase controlling device comprisingmeans for producing a rotary field, and a coil inductively related tosaid iield and adjustable as to its angle with respect to said iield.

4. ln a Wire signaling system subject to interference due to radiosignaling, an which a similar disturbing electromotive force may beimpressed for balancing purposes, a device associated with saidauxiliary circuit for adjusting the phase of the current resultin fromsaid balancing electromotive force au a device associated with saidauxiliary circuit for adjusting the amplitude of said current, saidphase controlling means comprising a pair of branch circuits each' havina coil, therein, means to cause 900 phase if @mams naigmoxhou 0i saidcoils anfl n fhird wil ing mir of branch cfcus arr'mlgs. cut said fieldai', any desnef coll tharem, mesma t@ cause n

